Diane Sawyer interviews Jaycee Dugard

For the first time, Jaycee Lee Dugard revealed new details about how she was abducted and kept as a sex slave for 18 years.

Dugard, now 31, was kidnapped from South Lake Tahoe in 1991 and held captive by Phillip and Nancy Garrido.

Dugard was a fifth grader who set out for the school bus one morning when she was kidnapped by convicted sex offender Phillip Garrido. He handcuffed her, raped her and imprisoned her in a backyard compound.

Three years into her captivity, at the age of 14, Dugard went into labor with the first of her daughters - fathered by Garrido.

In an exclusive interview with ABC News' Diane Sawyer, Dugard explained how she felt after giving birth.

"Very painful, but then I saw her. She was beautiful. I felt like I wasn't alone anymore," said Dugard. "I had somebody who was mine."

She gave birth again in 1997 to another little girl. She educated her children, creating a school in the compound to teach them as much as she could.

Asked how she was able to cope, Dugard said, "I don't know. I can't imagine being beaten to death, you know? And you can't imagine being kidnapped and raped. So, it's just, you just do what you have to do to survive."

She also thought about her mother every day. After her rescue in 2009, the two were finally reunited.

Terry Probyn recalls how she was rushing off to work on that fateful day 18 years ago, and says she regrets not saying goodbye to her daughter.

"I chose not to go in and kiss my girls goodbye that morning, wanting to be on time. For 18 years, I kick myself for not kissing that baby goodbye," said Probyn.

In a new memoir set to go on sale next week called "A Stolen Life," Dugard also reveals how Phillip Garrido told her she should be agreeable to having sex with him because it meant he wouldn't have to molest anyone else.

The Garridos pleaded guilty and received lengthy prison sentences earlier this year.